Combined Pre-Treatment and Causticization of Cotton Fabric for Improved Dye Uptake

Conventionally, cotton fabric is subjected to a series of separate pretreatment processes such as desizing, scouring, and bleaching to remove natural and added impurities for satisfactory dyeing and finishing. When the sole purpose is to improve the dye uptake, cotton fabric is subjected to yet another separate process called causticization, a treatment of cotton fabric at reduced concentration of caustic soda (110-150 g/L) compared to mercerization. All these processes i.e. desizing, scouring, and bleaching are lengthy and require large amount of water, energy, chemicals, and time which lead to increase in cost and productivity loss. In this paper, a combined desizing, scouring, bleaching and causticization process with shorter processing time is reported. Single factor randomized experimental design was used for process optimization. Based on experiments, the optimum recipe consisted of padding the gray cotton fabric using a twodip, two-nip technique in a bath containing NaOH 140g/L; Sodium Per Borate (SPB) 40-45g/L; wetting agent 1g/L, batching for 30 min at room temperature and washing the treated fabric with 1g/L emulsifier twice for 15 minutes each at boil with 3% owf SPB added during the second wash, rinsed with hot and cold water and air dried. The results showed excellent wettability, good degree of whiteness, minimum loss of tensile strength and higher dye uptake compared to uncausticized commercially bleached cotton fabric.